What things do you do to confuse/slightly annoy people that you find very funny?

My friends and I love to do very random things that we think are very funny, but most other people find stupid or obnoxious. As a general rule we try to not do anything that could harm someone or annoy them too much, but more confuse people and make the occasional passer-by smile. For instance:

Having 10 people split up in a few cars one night putting up approximately 15 large wooden signs around town, including one that just said "Hummus?", a "dolphin crossing" sign, and a "go" sign.

The Follow Game, in which we follow a car on the highway or around town until it gets incredibly awkward

I like to get a friend have them sit next to an unsuspecting coworker, or other friend, and agree to laugh at the punchline of a totally random joke. The unsuspecting person always laughs nervously, pretending that they get it, when we know for sure that they don't... goofy/corny, I know.. but fun as hell. This is the joke:

Q: How many pancakes can you fit in a dog house?? A: Fish Don't Eat Ice Cream!!